He is adopted by a childless couple, grows up within the tribe, eventually leaving to rejoin Roman society, and being carried along by a chain of events all the way to Rome and ultimately back to Britain.

Like many Sutcliff novels, the plot is driven by the protagonist's search for identity amidst several cultures in which he feels himself to be an outcast.

This scene is witnessed by Centurion Justinius, and results in Beric being condemned to work in the salt mines, a certain slow and painful death.

The progress of the Rhee Wall and the lives of the workers are threatened by a great storm, during which Beric bonds with his new comrades, and after which he concludes that he has finally found a place and a people where he belongs.

Like in many Sutcliff novels, the theme of Outcast revolves around Beric's struggle to find belonging as he is caught in various degrees of acceptance and discrimination by the various societies through which he travels.